Atrial pacing minimization in sinus node dysfunction and risk of incident atrial fibrillation: a randomized trial.

BACKGROUND AND AIMS: High percentages of atrial pacing have been associated with an increased risk of atrial fibrillation. This study is aimed at evaluating whether atrial pacing minimization in patients with sinus node dysfunction reduces the incidence of atrial fibrillation. METHODS: In a nationwide, randomized controlled trial, 540 patients with sinus node dysfunction and an indication for first pacemaker implantation were assigned to pacing programmed to a base rate of 60 bpm and rate-adaptive pacing (DDDR-60) or pacing programmed to a base rate of 40 bpm without rate-adaptive pacing (DDD-40). Patients were followed on remote monitoring for 2 years. The primary endpoint was time to first episode of atrial fibrillation longer than 6 min. Secondary endpoints included longer episodes of atrial fibrillation, and the safety endpoint comprised a composite of syncope or presyncope. RESULTS: The median percentage of atrial pacing was 1% in patients assigned to DDD-40 and 49% in patients assigned to DDDR-60. The primary endpoint occurred in 124 patients (46%) in each treatment group (hazard ratio [HR] 0.97, 95% confidence interval [CI] 0.76-1.25, P = .83). There were no between-group differences in atrial fibrillation exceeding 6 or 24 h, persistent atrial fibrillation, or cardioversions for atrial fibrillation. The incidence of syncope or presyncope was higher in patients assigned to DDD-40 (HR 1.71, 95% CI 1.13-2.59, P = .01). CONCLUSIONS: Atrial pacing minimization in patients with sinus node dysfunction does not reduce the incidence of atrial fibrillation. Programming a base rate of 40 bpm without rate-adaptive pacing is associated with an increased risk of syncope or presyncope.

Impact of Nationwide COVID-19 Lockdowns on the Implantation Rate of Cardiac Implantable Electronic Devices.

AIM: The COVID-19 pandemic resulted in a significant decrease in the number of hospital admissions for severe emergent cardiovascular diseases during lockdowns worldwide. This study aimed to determine the impact of both the first and the second Danish nationwide lockdown on the implantation rate of cardiac implantable electronic devices (CIEDs). METHODS: We retrospectively analysed the number of CIED implantations performed in Denmark and stratified them into 3-week intervals. RESULTS: The total number of de novo CIED implantations decreased during the first lockdown by 15.5% and during the second by 5.1%. Comparing each 3-week interval using rate ratios, a significant decrease in the daily rates of the total number of de novo and replacement CIEDs (0.82, 95% CI [0.70, 0.96]), de novo CIEDs only (0.82, 95% CI [0.69, 0.98]), and non-acute pacemaker implantations (0.80, 95% CI [0.63, 0.99]) was observed during the first interval of the first lockdown. During the second lockdown (third interval), a significant decrease was seen in the daily rates of de novo CIEDs (0.73, 95% CI [0.55, 0.97]), and of pacemakers in total during both the second (0.78, 95% CI [0.62, 0.97]) and the third (0.60, 95% CI [0.42, 0.85]) intervals. Additionally, the daily rates of acute pacemaker implantation decreased during the second interval (0.47, 95% CI [0.27, 0.79]) and of non-acute implantation during the third interval (0.57, 95% CI [0.38, 0.84]). A significant increase was observed in the number of replacement procedures during the first interval of the second lockdown (1.70, 95% CI [1.04, 2.85]). CONCLUSIONS: Our study found only modest changes in CIED implantations in Denmark during two national lockdowns.

Usefulness of echocardiography for predicting ventricular tachycardia detected by implantable loop recorder in syncope patients.

Ventricular tachycardia (VT) may lead to syncope and sudden cardiac death. Implantable loop recorders (ILR) are recommended in the clinical work-up of patients with unexplained syncope. Our aim was to evaluate if echocardiographic parameters assessed prior to ILR implantation in patients with unexplained syncope may aid in identifying individuals with an increased risk of VT. The present study included 288 ambulatory patients (mean age 58 ± 19 years, 51% women) with syncope (90%) and presyncope (10%) who had an ILR implanted in the diagnostic workup. All patients underwent an echocardiographic examination prior to device implantation (median 3 months [IQR 1 to 6 months]). We examined incident VT, defined as a first-time episode of VT (> 30 s) or non-sustained VT (< 30 s) detected by the ILR. During median follow-up of 2.9 years [IQR 1.3 to 3.5 years] of continuous rhythm monitoring, 36 patients (13%) were diagnosed with incident VT (n = 25 non-sustained VT, n = 11 sustained VT). In unadjusted Cox proportional hazards models, left ventricular (LV) mass index (HR: 1.04 per 1 g/m2 increase [1.00 to 1.08], P = 0.047), mean LV wall thickness (HR: 1.36 per 1 mm increase [1.08 to 1.71], P = 0.009), and global longitudinal strain (HR: 1.15 per 1% decrease [1.05 to 1.25], P = 0.002) were significantly associated with VT. After adjusting for age, sex, implantable loop recorder indication and known heart failure, the above-mentioned parameters remained significantly associated with incident VT. LV mass index, LV wall thickness, and GLS may aid in identifying patients with increased risk of incident VT among patients with syncope. Echocardiography may potentially help select patients who can benefit from ILR.

Sex differences in echocardiographic predictors of bradycardia detected by implantable loop recorder in patients with syncope and palpitations.

OBJECTIVE: Our aim was to investigate whether echocardiography may aid in identifying patients, specifically men, at risk of bradycardia as detected by implantable loop recorders (ILR) in patients evaluated for syncope and palpitations. METHODS: We included ambulatory patients undergoing ILR implantation for syncope (84%), presyncope (9%), and palpitations (8%). Echocardiographic examination was performed prior to implantation (2.9 months [IQR 1.0-6.0 months]). Echocardiograms were analyzed for conventional and speckle tracking parameters. We examined time to first event of bradycardia, defined as (a) heart rate <30 beats/min and (b) ≥4 beats, including sinus arrest, asystole, sinoatrial block, and second- and third-degree atrioventricular nodal block. We applied Cox proportional hazards models. RESULTS: A total of 285 patients we enrolled, and during a median time of 2.7 years [IQR 1.0, 3.3 years] of continuous heart rhythm monitoring, 84 (29%) had bradycardia detected by ILR. Patients with bradycardia were older (61 ± 19 years vs 55 ± 18 years, P = .01) and more frequently men (62% vs 44%, P = .01). Sex modified the association between echocardiographic parameters and bradycardia (P interaction <0.05 for all), such that left ventricular LV mass index (HR: 1.02 per 1g/m2 increase [1.01-1.04], P < .001), LV ejection fraction (HR: 1.04 per 1% decrease [1.01-1.08], P = .02), and global longitudinal strain (HR: 1.09 per 1% decrease [1.01-1.19], P = .03) were associated with bradycardia in men but not women (P > .05 for all in female). After adjusting for baseline clinical characteristics, medical therapy, and loop indication, the abovementioned parameters remained significantly associated with incident bradycardia in men. CONCLUSION: Echocardiographic parameters of LV structure and function may potentially be more useful for predicting bradycardia in men than women, among patients undergoing ILR implantation for syncope, presyncope, and palpations.

Cardiac repolarization during hypoglycaemia in type 1 diabetes: impact of basal renin-angiotensin system activity.

AIMS: Hypoglycaemia-induced cardiac arrhythmias may be involved in the pathogenesis of the 'dead-in-bed syndrome' in patients with type 1 diabetes. Evidence suggests that the renin-angiotensin system (RAS) influences the occurrence of arrhythmias. The aim of this study was to explore if basal RAS activity affects cardiac repolarization during hypoglycaemia, thereby potentially carrying prognostic information on risk of the 'dead-in-bed syndrome'. METHODS AND RESULTS: Nine subjects with high RAS activity and nine subjects with low RAS activity were subjected to single-blinded placebo-controlled hypoglycaemia (nadir plasma glucose 2.4 mmol/L). QTc/QTcF and QT dynamics were registered by Holter monitoring. QTc prolonged during [8 (+/-2.3) ms, P < 0.01] and after [11 (+/-3) ms, P < 0.001] hypoglycaemia. Dynamic QT parameters reacted ambiguously. Low RAS activity was associated with a slightly more pronounced QT prolongation [6 (+/-3) ms, P = 0.04]. Adrenaline tended to increase more in the low-RAS group (P = 0.08) and was correlated to QTc (r = 0.67, P < 0.01) and QTcF (r = 0.58, P < 0.05) during hypoglycaemia. CONCLUSION: Low basal RAS activity may be associated with a slightly more pronounced QT prolongation during hypoglycaemia, when compared with high RAS activity. The impact, however, is modest and the clinical consequence is unclear.

Cardiac repolarization during hypoglycaemia and hypoxaemia in healthy males: impact of renin-angiotensin system activity.

AIMS: Activity in the renin-angiotensin system (RAS) may influence the susceptibility to cardiac arrhythmia. To study the effect of basal RAS activity on cardiac repolarization during myocardial stress induced by hypoglycaemia or hypoxaemia in healthy humans. METHODS AND RESULTS: Ten subjects with high RAS activity and 10 subjects with low RAS activity were studied on three different occasions: (i) hypoglycaemia (nadir P-glucose 2.7 +/- 0.5 mmol/L), (ii) hypoxaemia (nadir pO(2) 5.8 +/- 0.5 kPa), and (iii) normoglycaemic normoxia (control day). QT parameters were registered by Holter monitoring. Hypoglycaemia and hypoxaemia induced QTc prolongation (P < 0.001, both stimuli). The QT/RR slope and the VR increased as a function of hypoglycaemia, but were unaffected by hypoxaemia. Low RAS activity was associated with a steeper QT/RR slope in the recovery phase after both stimuli: hypoglycaemia: P = 0.04; hypoxia: P = 0.03. RAS activity had no impact on QTc [P = 0.48 (hypoglycaemia) and P = 0.40 (hypoxaemia)] or any of the other outcome variables. CONCLUSION: Basal RAS activity has significant impact on QT dynamics, but not the corrected QT interval, during recovery from hypoglycaemia and hypoxaemia. The impact, however, is modest and more subtle than initially expected. The clinical relevance is unclear.